1. Field
The present disclosure relates generally to ceramic materials and, in particular, to structures containing multiple layers of ceramic materials. Still more particularly, the present disclosure relates to a method and apparatus for reworking a ceramic matrix composite sandwich structure to restore the capability of the structure to carry both in-plane and out-of-plane loads.
2. Background
Various types of vehicles require thermal resistance or thermal protection systems. For example, some of the exterior surfaces of spacecraft require a capability to withstand temperatures that may be encountered during re-entry of the spacecraft into the atmosphere. As another example, jet engines, rocket engines, and power generators also have surfaces that are required to be capable of withstanding the operating temperatures that occur during the use of engines and generators.
A ceramic matrix composite material is a ceramic material consisting of two or more components. A ceramic matrix composite material typically includes a ceramic matrix component with additional components being incorporated to strengthen, toughen, or enhance thermal, physical, or other properties. For example, ceramic matrix composite materials may consist of ceramic fibers embedded in a ceramic matrix, thus forming a ceramic fiber reinforced ceramic material. The matrix and fibers may consist of any ceramic material.
Ceramic matrix composite materials are able to withstand a variety of operating environments. For example, ceramic matrix composite materials are able to withstand the operating temperatures that occur during re-entry of a space vehicle or during the use of engines and generators as described above.
Structures made of ceramic matrix composite materials may be used in aerospace and many other applications. For example, ceramic structures may be used to fabricate parts that are subjected to exhaust gasses in aircraft and other applications. Tiles wrapped with ceramic matrix composite materials may be used as part of a thermal protection system on the surface of a spacecraft. Ceramic matrix composite structures also may be used in various components. For example, these components may include, without limitation, a nozzle or combustion chamber for an engine or generator.
Ceramic matrix composite materials may be used to make a variety of structures. For example, ceramic tiles may take the form of a ceramic substrate with a facesheet that is wrapped around and bonded to the ceramic substrate. The facesheet may include a number of layers of ceramic matrix composite materials. Thus, ceramic tiles and other ceramic structures may include layers of ceramic matrix composite materials.
One type of ceramic matrix composite structure is a ceramic sandwich structure. A ceramic sandwich structure may include facesheets formed from consolidated layers of a ceramic matrix composite material. The facesheets are bonded to opposite sides of an interior section or core made of ceramic matrix composite materials to form the ceramic sandwich structure.
In one example, the core of a ceramic sandwich structure may be created by an array of pins made of ceramic matrix composite materials. The ceramic pins are arranged to form a truss core support structure between the facesheets. The pins extend through the thickness of the core and penetrate the facesheets. The pins provide load paths along which various loads are transferred between the facesheets. Such loads may include compressive, tensile, or shear loads or any of these or other loads in any combination.
Inconsistencies may occur in ceramic sandwich structures during the manufacturing or use of such structures. These inconsistencies may include, for example, delamination of layers in a facesheet, a facesheet de-bonding from the substrate, an impact forming a dent or crack in a facesheet and extending into the ceramic core, or other types of inconsistencies. Currently, these inconsistencies may require reworking to restore the structure to a desired level of operation.
The traditional approach for reworking these types of structures is to replace them. For example, a part containing an inconsistency is removed and a new part is put in place of the old part. However, replacement of parts may be costly and time consuming. Parts containing ceramic matrix composite materials may be expensive. In addition to the replacement operation itself being time consuming, the needed parts may not be on hand or may need to be specially manufactured. The turn-around of a vehicle including such a structure may be limited or reduced until the replacement can be made.
Therefore, it would be advantageous to have a method and apparatus that takes into account at least some of the issues discussed above, as well as possibly other issues.